Pseudomonas aeruginosa and Serratia marcescens produce severe corneal infections which are difficult to treat and often result in extensive corneal scarring, corneal perforation, and visual impairment. The goal of the proposed research is to elucidate the mechanisms by which the corneal destruction characteristic of pseudomonas and serratia-induced corneal disease is produced. The approach which will be taken to clarify these pathological processes will be (a) to isolate and physicochemically characterize the extracellular, cornea-liquefying psedomonas and serratia proteases, (b) to define the mechanism(s) by which the proteases elicit corneal destruction, and (c) to determine if the proteases function to produce corneal damage during pseudomonas and serratia keratitis. The cornea-damaging proteases will be isolated in homogeneous states by sequential (a) ammonium sulfate precipitation, (b) ion-exchange, molecular sieve, and adsorption chromatography, and (c) isoelectric focusing. Experiments designed to determine the mechanisms by which the proteases cause corneal damage, and to determine if they play a role in the pathogenesis of pseudomonas and serratia-induced corneal disease, will indlude: (a) comparison, by light and electron microscopy, of the damage produced by the proteases with that produced by experimental corneal infections, (b) determining if the proteases can damage or kill polymorphonuclear leukocytes and corneal epithelial cells, keratocytes, and endothelial cells maintained in tissue culture, and cause the cells to release cornea-damaging substances, (c) quantitation, by immunological techniques, of the bacterial proteases present in the infected corneas, and (d) determining if active and/or passive immunization, or administration of protease inhibitors, protects against damage following challenge with the bacteria.